Method of making a muffler



Oct. 4;?11966 F. WHITE 3,276,108

METHOD oF MAKING A MUFFLER Filed Feb. 2l, 1964 2 Sheets-Sheet l lmlulgm:m.

' Patented Oct. 4, 1966 3,276,108 METHOD F MAKING A MUFFLER Frederick White, Richmond, Va., assgnor to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Filed Feb. 21, 1964, Ser. No. 347,077 Claims. (Cl. 29-157) This invention relates to a method of manufacture of a muliier such as is normally used to reduce noise from the exhaust of an internal combustion engine. A common f-orm of muffler construction comprises a box-like structure having inlet and outlet pipe connections arranged to interrupt the free flow of exhaust gas from the engine to the atmosphere and level out the -gas pulsations. A muflier is usually divided into a series of cham bers and exhaus-t gas is arranged to flow through perforated holes in a tubular member connecting successive chambers. In most cases of existing mufllers no special arrangements are made to cool the exhaust gas during its passage from muiiier inlet to outlet.

According to the present invention the muffler casing is comprised of tubed sheet. This is a corn-mon name given to laminated sheet in which ducted passages are formed between the laminations. By suitably arranging the position of the ducted passages and piercing holes in them exhaust gas is made to flow through them while passing from one chamber to another. In this manner the exhaust gas temperature is reduced by conduction of heat t-o the cool outer surface of .the muffler. A reduction in exhaust gas temperature will result in decreased volume and speed of gas ow. Another advantage of this inventi-on is that the construction of a muffler can be simpliiied because fewer parts are needed in its construction. A further advantage is that due to its improved heat conducting ability a muier of smaller dimensions is made possible.

Another object of this method is -t-o show a way to form apertures tinto the ducted passages of the tubed sheet before it is bent into shape to form the mutiier casing.

All the references to tubed sheet contained herein apply to a well known method whereby two sheets of metal are 'bonded together by a rolling process and subsequently separated locally in a predetermined pattern of ducts. The invention is not conllined to any particular method of manufacture of tubed sheet but rather to the application of such t-o muier construction. The invention has particular reference to aluminum tubed sheet because of its high heat conductivity and resistance to c-orrosion.

In the accompanying drawings FIG. l shows a longitudinal section through a muliier indicating by arrows the path of exhaust gas. FIG. 2 shows a cross section through the muliier taken along line A-A of FIG. 1 indicating ducted passages in its outer casing. FIG. 3 shows an enlarged section of a portion of the outer casing ducted passages which indicates the position of slots communicating with the muiiier interior. FIG. 4 shows a plan view of the tubed sheet from which the mutiier casing is constructed. FIG. 5 shows a sectional elevation of the tubed sheet in process of being slotted through the raised ducted passages. I'FIG. y6 shows a plan view of the inside surface of a tubed sheet while it is still in its rhat form before being bent to shape.

Now referring to FIG. 1, the pipe connection 1 is arranged t-o connect with the engine exhaust pipe to conduct exhaust gas into the iirst expansion compartment 2 and thence through slots .3 cut into ducted passages 4. The .first baiiie 5 which is sealed at f6 around its periphery, compels exhaust gas to 'follow va path adjacent to outer shell 7 of the muliier casing. Arrows indicate the path of the exhaust gas and it Will be seen that in passing from one chamber to another the gas contacts outer shell 7 of the muiiier casing through which it can release s-ome of its heat t-o the surrounding atmosphere. In the case of an automobile muffler, the added cooling of the muiiier due to the motion of the vehicle would help to increase muier efficiency. Ducted passages 4 are interrupted at y8 so as to force exhaust gas int-o the second expansi-on chamber 9 before entering ducted passages 10. Second baffle 11 is sealed to the inner surface of the mufer casing at l12 in a similar manner to the iirst baffle S. From ducted passages 10 the exhaust gas is lead through slots 13 into the third expansion chamber 14 and thence to pipe connection 415 which is connected to the exhaust tail pipe. `Both pipe connections 1 and 15 are securely fastened to the muffler casing at 16 and the ducted passages are shortened at 1'7 to provide a smooth surface for forming a gas tight joint.

FIG. 2 shows a section through the muier at line A-A of FIG. 1 and indicates at 18 where the tubed sheet is joined between adjacent ducted passages after bending to shape. FIG. 3 shows an enlarged section of the muiiier casing in which ducted passages 4 are formed by hydraulically separating the inner lamination 19 from outer shell 7. 'Slots 3 which are cut int-o ducted passages 4 are arranged in width and depth t-o give the desired degree of exhaust passage area without undue back pressure.

In one method of manufacturing tubed sheet the pattern of ducted passages is irst printed on to a sheet of metal using a graphite ink. After drying another sheet is placed on top covering the pattern and the two sheets are hot rolled together. After cooling the composite sheet is sheared t-o expose one end of the printed pattern and a tube is inserted at this point between the two sheets for connecting to a pump. The composite sheet is then placed in a press and hydraulic pressure from the pump inflates the ducted passages following the path of the printed pattern. The ducted passages can be raised from the composite sheet on both sides or from one side only. The drawings illustrating the invention of this applicati-on show the ducted passages formed on one side only.

(FIG. 4 shows -a plan view of the tubed sheet after hydraulically inflating a pattern of ducted passages. The hydraulic pressure is applied to tube inlet 20 through main ducted passage 21 raising the main groups Vof ducted passages 22 in the .flat tubed sheet 28. The size of tubed sheet 28 is made large enough to allow side 24 with ducted passages 21 to be sheared olf and the ends of ducted passages at 2'5 are attened down and sealed oft as shown in FIG. 6.

After shearing to size the tubed sheet is passed through a milling machine, shown in FIG. 5, where all the slots 3 are cut in one pass of the tubed sheet through the machine. The milling mach-ine comprises rigid supports -2'6 carrying roller 27 for supporting tubed sheet 28. A rotatable cutter spindle 29 supporting cutters 30, is positioned t-o cut slots `3 at the required depth without touching outer shell 7 of tubed sheet 28. -Bearings 31, free to rotate on cutter spindle 29, are arranged to contact the tubed sheet at 32 pressing against roller 27. Cutters 30 are locked to cutter spindle 29 and rotate with it. Roller 27 is rotated to drive tubed plate through the machine while slots are cut int-o successive ducted passages. FIG. i6 shows the tubed sheet 28 atter it has passed through the milling machine and the slots have been cut. The completed tubed sheet 28 is then bent into shape as shown in FIG. 2 and a suitable gas tight yjoint 1|8 (FIG. 2) formed along its whole length. -Pipe connections 1 and 15 als-o rst baille 5 and second baffle 3 11 are enclosed and sealed into the tubed sheet 28 as itis bent,

The invention is not contined to an application wherein exhaust gas is transferred through slots to the ducted passages as it would be equally effective if holes were used instead of slots. Alternatively, the slots into the ducted passages could vbe made longitudinally instead uo'f radially as shown in the drawings. In this latter case it would be necessary to seal ofrp the slots at points 6 and l12 where the two baflies 5 and 11 are iitted.

fHaving now `fully described one embodiment of the invention, what I claim is:

1. A meth-od of manufacturing a mutiler comprising 'the steps of forming a laminated sheet material having "bonded and unbonded areas and further having longitudinally extending marginal portions, inflating the unbonded areas to form passageways which extend longitudinally along the .laminated sheet, providing a plurality of apertures through the laminated sheet along the passageways formed by inilating the unbonded areas of said laminated sheet, bending said laminated sheet to form a longitudinal seam at the longitudinally extending marginal portions of said laminated sheet, and connecting inlet -and exhaust pipes to opposite ends of said bent laminated sheet.

2. A method of manufacturing a muler comprising the steps of forming a laminated sheet material having bonded and unb-onded areas and further having longitudinally extending marginal portions, inilating the unbonded areas to form passageways which extend longitudinally along the laminated sheet, providing a plurality of apertures through the laminated sheet along the passageways formed by initiating lthe unbonded `areas of said laminated sheet, bending said laminated sheet into tubular -form to provide a longitudinal seam at the longitudinally extending marginal portions of said laminated sheet and forming thereby an interior passageway, said apertures in said inflated portions of said laminated sheet providing communication between the longitudinally extending passageways formed by inflation of the unlbonded areas of said laminated sheet and the interior of the passageway formed by bending said laminated sheet into tubular form, and connecting inlet and exhaust pipes to opposite ends of said bent laminated sheet.

3. A ymethod of manufacturing a muler comprising the steps of forming a laminated sheet material having bonded and unbonded areas and further having longitudinally extending marginal portions, inflating the unbonded areas to Iform passageways which extend longitudinally along the laminated sheet, providing a plurality 'of apertures through the laminated sheet along the passageways formed by inflating the unbonded areas of said laminated sheet, bending said laminated sheet into tubular form to provide a longitudinal seam at the l-ongitudinally extending marginal portions of said laminated sheet and forming thereby an interior passageway, said apertures in said inflated portions of said laminated sheet providing communication between the longitudinally extending passageways formed by ination of the unbonded areas of said laminated sheet and the interior of the passageway formed by bending said laminated sheet into tubular form, securing bafe means t-o the inflated portions of said laminated sheet wvithin the interior passageway formed `by bending said laminated sheet into tubular form, and connecting inlet exhaust pipes to opposite ends of said bent laminated sheet.

4. A method lof manufacturing a muffler comprising the steps of forming a laminated sheet material having lunbonded areas of said laminated sheet, bending said laminated sheet into tubular form t-o provide a longitudinal seam at the longitudinally extending marginal portions of said laminated sheet and forming thereby an interior passageway, said apertures in said inated portions of said laminated sheet providing communication between the longitudinally extending passageways formed by ination of the unbonded areas of said laminated sheet and the interior passageway formed by bending said laminated sheet into tubular form, and connecting inlet and exhaust pipes to oppos-ite ends of said bent laminated sheet.

S. A method of manufacturing a muffler comprising the steps of forming a laminated sheet material having bonded and unbonded areas and further having longitudinally extending marginal portions, inflating the unbonded areas to `form a rst set of longitudinally extending passageways and a second set of longitudinally extending passageways which .are longitudinally spaced from said hrs-t set of -longitudinally extending passageways, providing a plurality of apertures through the laminated sheet along the passageways formed by inflating the unbonded areas of said laminated sheet, bending said laminated sheet into tubular form to provide a longitudinal seam at the longitudinally extending marginal portions of said laminated sheet and forming thereby an interior passageway, said apertures in said inflated portions of said laminated sheet provid-ing communication between the longitudinally extending passageways formed by iniiation of the unbonded `areas of said laminated sheet and the interior passageway formed by bending said laminated sheet into tubular form, securing baffle means to each set of the inflated portions of said laminated tsheet` within the interior passageway `formed by bending said laminated sheet into tubular form, and connecting inlet and exhaust pipes to opposite ends of said bent laminated sheet.

References Cited by the Examiner UNITED STATES PATENTS 1,402,896 1/1'9-22 Schneebeli 181-57 1,500,828 7/1924 Layne 29-163.5 X 2,016,254 10/ 19135 Noblitt et al. 181-46 2,054,703 9/1936 Little et al. 181-35 2,066,467 1/-1937 Gray 1-81-47 X 2,166,6- 7/ 1939 Martin 181-56 X 2,226,21-6 12/ 1940 -Breese 181-35 2,544,284 .3/ 1951 Stephens et al. 181-46 2,690,002 9/ 1954 Grenell 1811-35 2,906,006 9/ 1959 Neel 181-35 2,995,807 8/ 1961 Gibbs. 3,004,330 10/ 19611 Wilkins. 3,140,755 7/196-4 Tranel 181-35 3,166,829 1/196-5 Lemelson.

FOREIGN PATENTS 435,423 9/ 1935 Great Britain.

CHARLIE T. MOON, Primary Examiner. LEO SMILOW, R. S. WARD, Assistant Examiners. 

1. A METHOD OF MANUFACTURING A MUFFLER COMPRISING THE STEPS OF FORMING A LAMINATED SHEET MATERIAL HAVING BONDED AND UNBONDED AREAS AND FURTHER HAVING LONGITUDINALLY EXTENDING MARGINAL PORTIONS, INFLATING THE UNBONDED AREAS TO FORM PASSAGEWAYS WHICH EXTEND LONGITUDINALLY ALONG THE LAMINATED SHEET, PROVIDING A PLURALITY OF APERTURES THROUGH THE LAMINATED SHEET ALONG THE PASSAGEWAYS, FORMED BY INGLATING THE UNBONDED AREAS OF SAID LAMINATED SHEET, BENDING SAID LAMINATED SHEET TO FORM A LONGITUDINAL SEAM AT THE LONGITUDINALLY EXTENDING MARGINAL PORTIONS OF SAID LAMINATED SHEET, AND CONNECTING INLET AND EXHAUST PIPES TO OPPOSITE ENDS OF SAID BENT LAMINATED SHEET. 